stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Jason Greer on November 10, 2010, 10:24:24 AM
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I built this simple profile so that I would have a model to compete in one of our local profile meets. Design and build time was a little less than two weeks so it is nothing special. The filght qualities far exceeded my expectations and I was fortunate enough to win the advanced profile contest with it on its first outing. The model had never been put through a pattern before the contest. The details of the model are as follows:
wingspan: 57"
wing area: 650 sq in
weight: 54 ounces
motor: Scorpion 3026 710
battery: flightmax 5s 3000 (13.3 ounces)
esc: Phoenix ICE 50 lite in set RPM mode at 9600
propellor: 13x4.5 EP
64' x .015 lines
Power consumption is around 2000 mah for a 5:45 flight.
Jason
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Great Job Jason
looks like a cool profile too.
Norm Whittle
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Nice, very nice Jason.
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Thanks guys!
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Looks Good!!! I like it!!!!!!
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Thanks William!
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WTG Jason: big light and powerful - not a bad trade-off! CLP** HH%% #^
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Jason didnt tell you the rest of the story.
After Saturdays first 2 patterns in Proflle, he goes home and decorates it with a sharpie, comes back out and kicks more butt with it in Sunday's PA event.
LL~
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Dennis,
Thanks, it really exceeded my expectations.
Allan,
My sharpie sponsorship is still in the works, lol. It was a pleasure flying with you and congratulations on the well deserved pilots choice.
Jason
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Jason:
What is the total weight of the power package in your Eclipse?
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The total power system weight is about 22 ounces. The weight breakdown is:
motor: 7.2 ounces
battery: 13.3 ounces
esc: ~1 ounce
timer: maybe 10 grams
I haven't weighed the propellor that I am using, but the APC E props are very light.
Jason
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Since you are only using about 2/3 of battery capacity, could you get by with a smaller battery pack. How much weight might that save ?
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As a general rule a lipo should not be discharged past 75-80%. 80% of 3000 would be 2400. I could get by with a 2600 mah pack and that could save a couple of ounces. Since this was an uknown power system I wanted to err on the high side. In the future I am going to try some 67' lines and I will need to up the RPM a couple hundred to keep the same 5.4 second lap time. That will put me closer to using the full power available.
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Since you are only using about 2/3 of battery capacity, could you get by with a smaller battery pack. How much weight might that save ?
Allan, this is a very important question.
In addition to Jason's answer, you may want to read Dean's very informative and detailed post (reply #4) on the thread below.
http://stunthanger.com/smf/index.php?topic=19275.0
We have to keep in mind that the 75% rule is there ONLY as it pertains to a reasonable compromise between battery weight (physical size) AND the number of use cycles until battery death (battery death defined in ECL as that point that the battery at full charge has < 90% of its original capacity). With the new high tech. batteries from quality mfg. like Thunder power and Hyperion you can expect between 150 to 200 cycles when keeping the drain per flight at or below 75%. When using cheap batteries at 75%, you can expect a much lower cycle rate ( some reports are < 30) and marginal reliability. This 75% rule of thumb does NOT address the overhead issue we have in ECL.
Battery OVERHEAD:
Please read Dean's excellent post carefully. We need to always factor in this issue of OVERHEAD when selecting our battery size. We need to focus our math at the end of the flight when the power draining maneuvers come just when our battery has only <30% of it's power left. I will have a complete E-Stunt article on this in the next (JAN/FEB) issue of PAMPA SN. ....... Until then, please don't let the quest to save a few ounces compromise the power of your system at the very moment that max power is most needed! Remember the watts needed is around 175 to 200 watts per pound to do our maneuvers cleanly. Compute this with the V and mAh you have left near the END of the flight and you will see what I mean.
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Rudy,
Thanks for the much more elegant explanation.
Jason